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Effect of microwave power on EPR spectra of DOPA-melanin-netilmicin complexes with different drug concentrations : a study at temperatures in the range of 125-275 K

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Zdybel M. , Pilawa B. , Buszman E. , Wrześniok D. , Krzyminiewski R. , Kruczyński Z.

Nukleonika

2013

tom Vol. 58, No. 3

407--411

Electron paramagnetic resonance (EPR) spectra of the model eumelanin – DOPA-melanin complexes with netilmicin measured with a microwave power in the range 0.3–200 mW were examined. The influence of microwave power on amplitudes (A) and linewidths (ΔBpp) of the spectra was determined. The EPR spectra were recorded by a BRUKER spectrometer at temperatures 125, 175, 225 and 275 K. Continuous microwave saturation of EPR lines was used to compare the acceleration of spin-lattice relaxation processes in melanin samples. Changes of the parameters of the EPR spectra of DOPA-melanin-netilmicin complexes, with the microwave power for the samples differing in netilmicin concentrations, were observed. The effect of temperature on the changes of the EPR spectra of the analyzed melanin complexes with the microwave power was determined. The spin-lattice relaxation is faster at higher temperatures for all the tested melanin complexes.

Continuous microwave saturation of EPR spectra of melanin complexes at different temperatures

88%

Zdybel M. , Pilawa B. , Buszman E. , Wrzesniok D. , Krzyminiewski R. , Kruczynski Z.

Polish Journal of Medical Physics And Engineering

2011

tom 17

nr 2

85-94

Paramagnetic centers in DOPA-melanin and complexes of DOPA-melanin with netilmicin and Cu(II) were studied by the use of an X-band (9.3 GHz) electron paramagnetic resonance (EPR) spectroscopy. Measurements of continuous microwave saturation of EPR spectra at temperatures: 125 K, 175 K, 225 K, 275 K, were performed. Homogeneous broadening of all the examined EPR spectra was observed. EPR spectra of DOPA-melanin-Cu(II) complexes saturated at higher microwave powers than the others tested melanin samples. Fast spin-lattice relaxation exists in DOPA-melanin-Cu(II) complexes. Slow spin-lattice relaxation processes exist in melanin's paramagnetic centers of DOPA-melanin and its complexes with netilmicin, and its complexes with both netilimicin and Cu(II). EPR spectra of all the tested samples saturated at higher microwave powers with increasing of the measuring temperature. Faster spin-lattice relaxation processes occurs in DOPA-melanin and its complexes with netilmicin and Cu(II) at higher temperature.

Terapia fotodynamiczna nowotworów upigmentowanych. Modelowanie własności optycznych melaniny metodami Monte Carlo

75%

Matuszak Z. , Sawow A. , Wasilewska-Radwańska M.

Bio-Algorithms and Med-Systems

2005

tom Vol. 1, no. 1/2

237--240

Z użyciem metody Monte Carlo wykonano symulacje krzywej absorpcji wodnych roztworów DOPA-melaniny i porównano z krzywymi otrzymanymi doświadczalnie. Własności optyczne pojedynczych cząsteczek melaniny traktowanych jako sfery o określonym promieniu zostały obliczone na podstawie teorii Mie,go. Zbadano wpływ rozmiarów cząsteczek melaniny oraz rodzaju generatorów liczb przypadkowych na jakość symulacji krzywych absorpcji metodą Monte Carlo. Stwierdzono dobrą odtwarzalność charakteru zaniku krzywej absorpcji, obie krzywe doświadczalna i wysymulowana miały podobny eksponencjalny charakter zmian intensywności w funkcji długości fali, jednak wartość nachylenia przebiegu dla krzywych wsymulowanych była systematycznie mniejsza.

Monte Carlo (MC) simulations of the absorption curves of the aqueous solution of DOPA-melanin were performed and compared with experiment results. The simulations of the optical properties of individual melanin particles treated as spheres were performed according to the Mie theory. The influence of the melanin particles diameters and the type of the random numbers generators on quality of Monte Carlo simulations was investigated and briefly discussed. The MC simulation gave good reproducibility of the exponential character of absorbance dependence on wave-length, but the inclination of the simulated absorption curve was systematically smaller comparing to experimental one.